Topological diversity of artificial β-barrels in water

✍ Scribed by Gopal Das; Stefan Matile

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 223 KB
• Volume: 13
• Category: Article
• ISSN: 0899-0042
• DOI: 10.1002/1520-636x(2001)13:3<170::aid-chir1016>3.0.co;2-6

✦ Synopsis

Rigid-rod ␤-barrels are composed of interdigitating, short, amphiphilic peptide strands flanked by stabilizing rigid-rod "staves". We here report studies on the topological diversity of these recently devised artificial ␤-barrels with regard to their length. For this purpose, homologous p-octiphenyl, p-sexiphenyl, and p-quarterphenyl rods were equipped with complementary tripeptide strands based on the sequences Lys-Leu-Lys and Glu-Leu-Glu. The stability of rigid-rod ␤-barrels of different length was determined by denaturation with guanidinium chloride. Free energies of ⌬G H2O = -5.2 kcalmol -1 , ⌬G H2O = -2.9 kcalmol -1 , and ⌬G H2O < -0.3 kcalmol -1 found for homologous p-octiphenyl, p-sexiphenyl, and p-quarterphenyl ␤-barrels demonstrated strong dependence of ␤-barrel stability on ␤-barrel length. These results revealed a very qualitative minimal (∼23 Å) and an "ideal" ␤-barrel length (∼34 Å), synergistic formation (␣ = 1.4) and remarkable stability for "ideal" p-octiphenyl ␤-barrels exceeding that of several proteins and most synthetic models. Rigid-rod ␤-barrels with p-oligophenyl "staves" longer than ∼34 Å will be very difficult to make and study because of rapidly decreasing rod solubilities. However, a strategy to bypass this apparent upper limitation of ␤-barrel length is introduced: supramolecular matching of mismatched rods yielded elongated ␤-barrels (61 Å) of acceptable stability (⌬G H2O = 2.2 -3.1 kcalmol -1 ).